Cranchiidae

File:Calmarcolossal.jpg's size allows it to feed on comparatively large prey compared to other cranchiids, but the prey it feeds on are still relatively small compared to its body size, comprising of chaetognaths, other squid, and fish up to the size of toothfishes.{{Cite journal|last1=Remeslo|first1=Alexander|last2=Yukhov|first2=Valentin|last3=Bolstad|first3=Kathrin|last4=Laptikhovsky|first4=Vladimir |name-list-style=amp |date=May 2019|title=Distribution and biology of the colossal squid, Mesonychoteuthis hamiltoni: New data from depredation in toothfish fisheries and sperm whale stomach contents|journal=Deep Sea Research Part I: Oceanographic Research Papers|volume=147|pages=121–127|doi=10.1016/j.dsr.2019.04.008|bibcode=2019DSRI..147..121R|s2cid=146043830}}{{Cite journal|title = Colossal squid vs huge toothfish – clash of the deep-sea titans|url = https://www.newscientist.com/article/dn27701-colossal-squid-vs-huge-toothfish-clash-of-the-deep-sea-titans/|access-date = 2 August 2015|first = Penny|last = Sarchet|date = 11 June 2015|website = New Scientist|doi = 10.1080/00222933.2015.1040477| bibcode=2015JNatH..49.2483R |s2cid = 82152308}}{{Cite journal|last1=Lu|first1=C.C.|last2=Williams|first2=R. |name-list-style=amp |date=June 1994|title=Contribution to the biology of squid in the Prydz Bay region, Antarctica |journal=Antarctic Science|volume=6|issue=2|pages=223–229|doi=10.1017/s0954102094000349|bibcode=1994AntSc...6..223L|s2cid=130139281 }}]]

The family is characterised by an enlarged mantle and short arms that bear two rows of suckers or hooks, with the third pair of arms often enlarged. Eye morphology varies widely, ranging from large and circular to telescopic and stalked. Recent studies have revealed that certain cranchiid squids, such as Galiteuthis glacialis, possess photophores—light-producing organs—on their eyes{{Cite journal |last1=Holt |first1=Amanda L. |last2=Sweeney |first2=Alison M. |date=June 2016 |title=Open water camouflage via 'leaky' light guides in the midwater squid Galiteuthis |journal=Journal of the Royal Society, Interface |volume=13 |issue=119 |pages=20160230 |doi=10.1098/rsif.2016.0230 |issn=1742-5662 |pmc=4938086 |pmid=27278362}}. These photophores emit bioluminescence that matches the intensity of downwelling sunlight, effectively masking the squid's silhouette from predators below. This counter-illumination strategy is a sophisticated form of camouflage in the mesopelagic zone. The photophores consist of laminated, fiber-like cells with semi-coaxial protein-dense layers surrounding axial cytoplasm, enabling precise control over light emission. The only organ that is typically visible through the transparent tissues is a cigar-shaped digestive gland, a cephalopod analogue of the liver; this organ is usually held in a vertical position to reduce its silhouette. Many species are bioluminescent and may possess light organs on the lower tip of their digestive gland and on the undersides of their eyes, used to cancel their shadows and evade predators.Mark Norman 2000. Cephalopods: A World Guide. Hackenheim, ConchBooks, p. 156.{{cite web|url=http://tolweb.org/notes/?note_id=835|title=Cranchiid Buoyancy|author=Richard E. Young|publisher=The Tree of Life Web Project|access-date=March 14, 2012}}{{Additional citation needed|date=March 2025}} Cranchiids have lower activity levels and metabolic rates than other families of squid, being more sedentary.{{cite journal |title=Functional traits explain trophic allometries of cephalopods |journal=Animal Ecology |date=7 September 2020 |volume=89 |issue=11 |doi=10.1111/1365-2656.13333 |url=https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2656.13333 |access-date=20 March 2025 |last1=Murphy |first1=Kieran J. |last2=Pecl |first2=Gretta T. |last3=Richards |first3=Shane A. |last4=Semmens |first4=Jayson M. |last5=Revill |first5=Andrew T. |last6=Suthers |first6=Iain M. |last7=Everett |first7=Jason D. |last8=Trebilco |first8=Rowan |last9=Blanchard |first9=Julia L. |pages=2692–2703 |pmid=32895913 |bibcode=2020JAnEc..89.2692M }}

A large, fluid-filled coelomic cavity containing ammonia solution is used to aid buoyancy.{{cite journal |last1=Clarke |first1=MR |last2=Denton |first2=EJ |last3=Gilpin-Brown |first3=JB |date=1979 |title=On the use of ammonium for buoyancy in squids. |journal=J Marine Biology Association United Kingdom |volume=59 |issue=2 |pages=259–276 |doi=10.1017/S0025315400042570|bibcode=1979JMBUK..59..259C }} This buoyancy system is unique to the family and is the source of their common name "bathyscaphoid squid", after their resemblance to a bathyscaphe. This system appears to develop further as cranchiids mature and move from surface waters to bathypelagic zones.{{Cite journal |last=Arkhipkin |first=Alexander |date=1996 |title=Age and growth of planktonic squids Cranchia scabra and Liocranchia reinhardti (Cephalopoda, Cranchiidae) in epipelagic waters of the central-east Atlantic |url=https://academic.oup.com/plankt/article-lookup/doi/10.1093/plankt/18.9.1675 |journal=Journal of Plankton Research |language=en |volume=18 |issue=9 |pages=1675–1683 |doi=10.1093/plankt/18.9.1675 |issn=0142-7873}} By consolidating ammonia in one compartment, they minimize energy costs associated with staying neutrally buoyant.{{Cite journal |last1=Kremer |first1=Kira Izabela |last2=Hagen |first2=Wilhelm |last3=Oesterwind |first3=Daniel |last4=Duncan |first4=Sabrina |last5=Bode-Dalby |first5=Maya |last6=Dorschner |first6=Sabrina |last7=Dudeck |first7=Tim |last8=Sell |first8=Anne F. |date=February 2025 |title=Trophic ecology of squids in the Benguela Upwelling System elucidated by combining stomach content, stable isotope and fatty acid analyses |journal=Marine Biology |language=en |volume=172 |issue=2 |doi=10.1007/s00227-024-04592-2 |issn=0025-3162|doi-access=free }} Observations suggest that juveniles maintain lower ammonium levels in the sac, possibly reflecting foraging in shallower habitats, whereas adults exhibit higher concentrations for stable flotation in deeper depths.{{Cite journal |last1=Voight |first1=J. R. |last2=Pörtner |first2=H. O. |last3=O'Dor |first3=R. K. |date=January 1995 |title=A review of ammonia-mediated buoyancy in squids (cephalopoda: Teuthoidea) |url=https://www.tandfonline.com/doi/abs/10.1080/10236249409378917 |journal=Marine and Freshwater Behaviour and Physiology |language=en |volume=25 |issue=1–3 |pages=193–203 |doi=10.1080/10236249409378917 |bibcode=1995MFBP...25..193V |issn=1023-6244}}

Cranchiids occupy a variety of trophic levels, with some species relying heavily on mesopelagic crustaceans such as copepods and small fishes; cranchiids as a whole may prey on a broad variety of species. Recent research using fatty acid and stable isotope analyses has shown that smaller cranchiids in the Benguela Upwelling System feed at mid to lower trophic levels, whereas larger, more muscular squid such as Todarodes and Abraliopsis occupy higher trophic positions; the ecological niche of cranchiids has even been compared to those of planktonic siphonophores.{{Cite journal |last1=Kremer |first1=Kira Izabela |last2=Hagen |first2=Wilhelm |last3=Oesterwind |first3=Daniel |last4=Duncan |first4=Sabrina |last5=Bode-Dalby |first5=Maya |last6=Dorschner |first6=Sabrina |last7=Dudeck |first7=Tim |last8=Sell |first8=Anne F. |date=2025-01-28 |title=Trophic ecology of squids in the Benguela Upwelling System elucidated by combining stomach content, stable isotope and fatty acid analyses |journal=Marine Biology |language=en |volume=172 |issue=2 |pages=32 |doi=10.1007/s00227-024-04592-2 |issn=1432-1793|doi-access=free }} Early juveniles may also exploit productive surface waters for faster growth before transitioning to deeper zones.{{Cite journal |last=Arkhipkin |first=Alexander |date=1996-01-01 |title=Age and growth of planktonic squids Cranchia scabra and Liocranchia reinhardti (Cephalopoda, Cranchiidae) in epipelagic waters of the central-east Atlantic |url=https://academic.oup.com/plankt/article-abstract/18/9/1675/1515104?redirectedFrom=fulltext |journal=Journal of Plankton Research |volume=18 |issue=9 |pages=1675–1683 |doi=10.1093/plankt/18.9.1675 |issn=0142-7873}} Because of their lower activity levels, the family is thought to comprise ambush predators.

As they develop, glass squids often exhibit a two-phase life cycle: juveniles in the epipelagic layers, then migrating into bathypelagic waters as adults.{{Additional citation needed|date=March 2025}} By remaining translucent and harnessing specialized buoyancy mechanisms involving ammonia retention, cranchiids reduce energy expenditure and adapt to low-light deep-sea habitats. This vertical migration strategy is thought to minimize predation risk while maximizing feeding opportunities.{{Citation needed|date=March 2025}}

In terms of reproduction, Galiteuthis glacialis (one such example of Cranchiidae) exhibits unique strategies adapted to the deep-sea environment. Spawning occurs in the bathypelagic zone, where females release eggs in a single batch—a process known as synchronous ovulation{{Cite journal |last1=Laptikhovsky |first1=Vladimir V. |last2=Fock |first2=Heino |last3=Piatkowski |first3=Uwe |last4=Schwarz |first4=Richard |last5=Hoving |first5=Henk-Jan T. |date=2019-05-31 |title=Reproductive strategies of deep-sea squid (Mastigoteuthidae, Chiroteuthidae, Batoteuthidae and Cranchiidae) |url=https://link.springer.com/article/10.1007/s00227-019-3532-2 |journal=Marine Biology |language=en |volume=166 |issue=7 |pages=85 |doi=10.1007/s00227-019-3532-2 |issn=1432-1793}}. Post-spawning, females undergo tissue degeneration, leading to increased buoyancy and causing them to ascend toward the surface. This phenomenon may explain the higher capture rates of mature females compared to males, which are hypothesized to die and sink to the seafloor after mating.

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The family contains two subfamilies (both established by Georg Johann Pfeffer) and about 15 genera:{{cite web|url=http://tolweb.org/Cranchiidae|title=Cranchiidae Prosch, 1847. Bathyscaphoid squids|first1=Richard E. |last1=Young |first2=Katharina M. |last2=Mangold (1922-2003)|year=2008|publisher=The Tree of Life Web Project|access-date=March 14, 2012}}

• Subfamily Cranchiinae
• Genus Cranchia
• Genus Leachia
• Genus Liocranchia
• Subfamily Taoniinae
• Genus Bathothauma
• Genus Belonella
• Genus Egea
• Genus Galiteuthis
• Genus Helicocranchia
• Genus Liguriella
• Genus Megalocranchia
• Genus Mesonychoteuthis
• Genus Sandalops
• Genus Taonius
• Genus Teuthowenia
• Parateuthis tunicata (incertae sedis){{Cite web |title=WoRMS - World Register of Marine Species - Parateuthis tunicata Thiele, 1921 |url=https://www.marinespecies.org/aphia.php?p=taxdetails&id=342379 |access-date=2023-04-12 |website=www.marinespecies.org}}

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{{CephBase Family|Cranchiidae}}

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Category:Cranchioidea